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June 2004

Beyond film

New digital cameras fix flaws without a PC


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It's all about making it easier for people to capture and share and relive their memories.

by Jamie Beckett

When digital cameras were first introduced, camera makers strove just to match the resolution and image quality of traditional film cameras. Now, thanks in part to research from HP Labs, HP's newest digital cameras have capabilities film photographers only dream about.

The Photosmart R707, introduced in May, inaugurated a new line of cameras that are able to eliminate red-eye, stitch together panorama photos in preview mode and produce pictures closer to what our eyes see -- all inside the camera, without a PC.

"HP has been driving the pace of new technologies in digital image science for years," says Frank Carau, technology research manager for HP Digital Cameras. "Our scanners, printers and digital cameras show the results."

New capabilities

HP Labs began feeding the technology pipeline for digital cameras as early as 1997.

"Initially, our research was focused on getting the color right, improving sharpness and contrast -- those were the big issues," says Dan Tretter, a researcher in the Imaging Systems Lab. "On the hardware side, resolution was the big issue."

Although mainstream digital cameras have not yet exceeded the resolution (measured by apparent sharpness and visible detail) of high-quality film cameras, the quality of digital has improved so much that the difference is indistinguishable for the common 4 x 6 prints.

As a result, researchers shifted their focus to building on digital’s strengths.

"Digital cameras can do things film cameras can't," says Qian Lin, manager of the Imaging Technology Department in HP Labs. "They can capture a wider area than optical-lens cameras are physically capable of. They can capture high-resolution video with sound. In the future, we think cameras will have more processing power and be able to actually 'understand' what they've captured."

Real Life technologies

For HP's new cameras, researchers in the company's imaging business and in HP Labs in Palo Alto, Calif.; Bristol, England and Haifa, Israel together created a package of advancements called Real Life technologies, all aimed at making it easier to take crisp, real-to-life photos.

Driven by an image engine co-developed by scientists at HP and Texas Instruments, Real Life technologies encompass not only in-camera red-eye removal and panorama preview, but also adaptive lighting to bring faces out of the shadows and details out of backgrounds in high-contrast photos, image advice and an image noise filter.

Some of the technologies appearing for the first time in the R707 include:

In-camera red-eye removal

No red-eye removal Red-eye removal on
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Red-eye occurs when the eye's retina reflects the camera's flash. It's particularly a problem in digital cameras because the flash and the lens are typically closer together than in film cameras, which reflects more light into the eye.

Most digital cameras have a pre-flash that reduces red-eye, but it also requires subjects to remain posed throughout a series of flashes, resulting in a subject who, all too often, has moved out of the pose or blinked and is photographed with their eyes shut.

When researchers began work on red-eye removal, their initial goal was to develop a software tool that allows a user to select a region containing a red-eye and correct the red tint.

Since refined, the patented algorithm now works automatically, locating apparent red areas in a photograph, then performing tests to determine whether that red is part of a human eye. If so, the algorithm removes it and previews the changes on the camera's LCD screen. Users may accept or reject the changes before saving the photo.

Walter S. Mossberg, the Wall Street Journal "Gadgets" columnist, and his assistant recently reviewed the R707’s red-eye correction capabilities for the newspaper. "We came away positively impressed," he wrote.

Adaptive lighting

Adaptive lighting technology off Adaptive lighting technology on
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The eyes and brain naturally deal with very high-contrast scenes -- those with dark shadows or bright areas. HP's Adaptive Lighting technology uses these same processing principles to adjust previously difficult images such as skiers in the snow or someone indoors standing in front of a window.

"One of the most common photography problems is back-lit photos," says Tretter. "When you take a picture, you don't want to have to worry if there's a window behind the person, or what direction the sun is coming, or if person is standing in shade."

Adaptive Lighting, developed by a team from HP's imaging business and HP Labs, "re-lights" photos at the moment they're shot to preserve life-like contrasts. Trying to perform the same task using imaging software is both difficult and less effective because critical picture information is lost when the image is compressed to a JPEG and downloaded to a computer. Adaptive Lighting processes all the data when re-lighting an image.

(Adaptive Lighting debuted in the HP Photosmart 945, the world's first camera to use Retinex theory so photos look more like what our eyes see. Four patents are pending on this technology.)

In-camera panoramic view

Today, digital photographers can take several photographs in sequence and use PC software to stitch them together into one panoramic shot. But post-production work takes time, and it’s difficult to get good results.

People often get home only to find that they've missed an important part of the image, the images aren't aligned properly or something else went wrong while taking the photos. At that point, it's too late.

The in-camera panorama preview features up to five images in a series, automatically aligning and merging the edges of each subsequent photo into one continuous shot. Photographers can preview and scroll this panoramic view on the camera's display screen to immediately determine if something went wrong. If so, they have a chance to re-shoot the scene. To make these factors consistent across each photo within the series, the camera automatically manages color, exposure and zoom. (To see panoramic images or read more about the research behind this, go here.)

HP adaptive demosaic technology

This accurately fills in full color information for every pixel, creating crisp, sharp images with outstanding resolution. For digital still cameras, color is usually captured by placing a red, green, or blue filter over each pixel in a checkerboard pattern known as a mosaic.

Next, a "demosaic" algorithm fills in the missing two-thirds of the color information. Obviously, filling in this much information makes the quality of the final photo entirely dependent upon the demosaic algorithm.

Most digital cameras use a demosaic algorithm that averages nearby measured pixel values along horizontal or vertical directions to estimate missing color information. This method leads to excellent resolution in vertical and horizontal directions but poor resolution along a diagonal image.

By contrast, HP's Adaptive Demosaic uses a decision equation to pick one of 256 possible averages of the nearby measured color values. This set of averages covers all possible orientations of image edge detail so that images have excellent resolution in horizontal, vertical and diagonal directions.

Image advisor

An incorrect white balance A corrected white balance
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This analyzes photos for problems such as over or under exposure or fuzzy focus and displays feedback on how to adjust settings to create a better picture in future shots. (Above: The photo on the left has a problem with white balance. In the photo on the right, the problem has been corrected.)

Future technologies

HP scientists continue their efforts to make HP's cameras even smarter. For example, cameras already have the ability to record what time a photo was taken, by which camera, at what focal distance and at what exposure -- information that helps people search and retrieve images, says Department Manager Lin.

"We want to go beyond that," she adds. The team is working to expand the metadata included in photo files to include where the picture was shot, which direction the camera was pointing and other similar information.

They're also investigating face detection so that photo files will be able to indicate if there are faces in the picture, and if so, how many. Other explorations include a "translating camera" that translates signs as users photograph them and technologies that make it easy to add audio, video, music and other media to a photograph.

"It's all about making it easier for people to capture and share and relive their memories" Lin says.

Related links

» Imaging Systems Lab
» Panorama preview research

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